1. Technical Field
This invention relates generally to electrical blade fuses, and more particularly for blade fuses for use in higher voltage applications.
2. Background of the Invention
Electrical blade fuses are well-known in the art. The modem electrical blade fuse was perfected by Littelfuse, Inc., the assignee of the present invention, and was described in many patents by the assignee. These patents include but are not limited to, Littelfuse""s U.S. Pat. Nos. 3,909,767; 4,023,265; 4,131,869; 4,580,124; 4,604,602; 4,635,023; 4,661,793; 4,997,393; 5,139,443; 5,663,861; and 5,668,521.
Some of fuses described in these patents include either a V-shaped or a sinusoidal-shaped fuse link. One example of such a V-shaped fuse link is that shown in U.S. Pat. No. 4,131,869. The V-shaped fuse link is shown as item 20 in FIG. 13 of the ""869 patent, and is described at column 6, line 56, through column 7, line 18 of the ""869 patent.
As is well-known in the art, blade fuses of the types shown in the above-referenced patents protect electrical circuits from current overloads. This protection results from the creation of a short in the fuse, and therefore in the circuit protected by the fuse, upon certain current or voltage overload conditions. Particularly, the fuse link breaks or opens upon current overload during a predetermined length of time.
Many of these blade fuses are extensively used in automobiles, and are therefore designed to be rated for service between 14 and 30 volts. Now, however, automobile manufacturers are designing more electrical accessories into automobiles, and are also designing or contemplating vehicles that use electrical motors, rather than internal combustion engines, for propulsion. Both of these developments increase the electrical demands upon current and future vehicles. As a result, circuits rated at up to 60 volts are now being contemplated for automobiles.
When the fusible link opens in fuses like those of the ""869 patent, especially those rated at between 14 and 30 volts, an arc forms between the burnt ends of the fusible link. At these lower voltages, the arc will not cause serious damage to the metal and plastic portions of the fuse. At higher voltages, however, extensive damage to the metal and plastic portions of the fuse can occur.
The invention is a blade fuse having a housing section and a fusible element. The housing includes an insulating portion or tab extending from the housing section, and disposed between opposite ends of the fusible element.
One aspect of the invention is directed to a blade fuse where the insulating tab is integral with the housing. In another aspect of the invention, the insulating tab is integral with the head portion of the housing.
In yet another aspect of the invention, the insulating tab extends downwardly from the head portion.
Another aspect of the invention is a one-piece, metallic element for a blade fuse. The blade fuse element has a fusible link and a pair of terminals. The fusible element extends above, rather than between, the terminals. Preferably, the one-piece metallic element is constructed in a manner wherein the thickness of the fusible link is thinner than the thickness of the terminals.
There are two preferred ways that the fusible link may be made thinner than the terminals. The first is by a skiving process, and the second is by a coining process.
While the one-piece metallic element may be made of any suitable metal, a preferred metal for the metallic element is a zinc alloy. In any event, the metallic element must be of a character that it is suitable for use in a fuse having voltage ratings of up to sixty volts.
In a preferred embodiment of the invention, the one-piece metallic element has a fusible link whose height is greater than the height of the terminals.
Yet another embodiment of the invention is a fuse comprising the above-referenced one-piece metallic element, and further comprising a housing to enclose the metallic element. The housing includes an insulating tab extending from the housing. The tab is disposed between opposite ends of the fusible element. The insulating tab acts as an arc barrier.